Annulus flooding detection system in flexible pipes using gamma rays transmission technique

Flexible pipes are modular constructions made up of several layers. They are broadly employed in oil & gas industry, playing an important role in the Brazilian Pre-Salt production. Under specific conditions, seawater can ingress and this contact with metallic middle layers can significantly lead to a service life reduction of these layers, especially due to a mechanism known as CO₂ Stress Corrosion Cracking (SCC-CO₂). Therefore, it becomes mandatory that inspection systems suitable for submarine use in order to detect annulus flooding before the failure of the flexible pipe become available. This paper presents an inspection system based on the gamma rays transmission focused on detecting such flood condition, possibly overcoming limitations of other inspection systems available in the market. The reliability of this solution was statistically evaluated as presented herein, showing great robustness based on the numerous available trials.